In the past, blocking of resin pellets has been a problem, so that various measures have been taken.
Patent Document 1 discloses that anti-adhesive powder is attached on the surface of EVA particles in a post-treatment step of the manufacturing process of resin pellets having ethylene-vinyl acetate copolymer particles as a base material by feeding EVA particles which have been cut in water into a transportation tube, and contacting with an anti-adhesive powder slurry in the transportation tube. It is described to be found that blocking is not occurred by such a manner even though a large amount of resin pellets are accumulated in a large hopper.
Patent Document 2 discloses that EVA microparticles is attached on the surface of EVA particles in a post-treatment step of the manufacturing process of resin pellets having EVA particles as a base material by adding an aqueous EVA dispersion into circulating water used for transportation of EVA particles, and the resulting resin pellets are further attached EVA particles even in the step of free feeding of resin pellets by spraying the aqueous EVA dispersion. In this manner, it is described that decrease in anti-blocking performance due to detachment of EVA microparticles in a free feeding pipe of resin pellets is suppressed, and reduction of the pressure loss and pinching of resin pellets to a rotary valve fitted in the free feeding pipe are prevented.
Patent Document 3 discloses a poor crystalline copolymerized polyester resin pellet having a glass transition point of equal to or more than 40 degrees centigrade. This resin pellet is coated with a powder layer of a copolymerized polyester resin having a glass transition point of equal to or more than 40 degrees centigrade and an average particle size of equal to or less than 35 μm, and capable of being dissolved in a general-purpose solvent. In this manner, it is described in such a manner that blocking of pellets is prevented, blocking is not occurred over a long period of time and the solution stability is excellent even though the resin is dissolved in a general-purpose solvent.
Patent Document 4 discloses that the emulsion polymer latex and the hardened tallow fatty acid are respectively attached to polymer particles by mixing an emulsion polymer latex to a slurry containing a (meth)acrylic block copolymer before mixing a hardened tallow fatty acid thereto, and heating at a predetermined temperature. In this way, it is described that blocking of adhesive resin pellets having a small hardness is thus suppressed.
Patent Document 5 discloses a surface treatment method of resin pellets. In this method, first, octadecyl isocyanate (1.0 equivalent in terms of the functional group) as a long-chain alkyl compound was polymerized with polyvinyl alcohol (degree of polymerization: 1,100, content of vinyl alcohol units: 98 mole %) as a saponified material of a polyvinyl acetate (co)polymer, to give a releasing agent component. Subsequently, this releasing agent component, an ethylene-acrylic acid copolymer as an acid-modified polyolefin copolymer and the like are put into water, and then heat-melted at 120 degrees centigrade in advance. Subsequently, its heat-melted material and water are uniformly emulsified and dispersed at 135 degrees centigrade, and cooled to give a desired aqueous releasing agent composition. With the use of such a method, it is possible to easily obtain resin pellets having excellent anti-blocking performance, without occurring separation, precipitation, clogging or the like even after obtaining a final product, and without deteriorating final performance of the final product.